U.S. Pat. No. 6,317,051 is considered to be the closest prior art. It discloses a water flow monitoring system for determining the presence of leaks in piping having water flowing therethrough under high pressure. The system includes a flow monitor mounted on a pipe for sensing the flow of water through the pipe. There is also provided a controller, composed of a timer and/or an accumulated volume meter associated with the flow monitor, to determine when the flow has continued for a pre-selected period of time, and/or when the amount of water has exceeded a pre-selected accumulated volume threshold, and logic components responsive to changes in flow rate. Upon detection of flow for the pre-selected period of time, and/or pre-selected accumulated volume threshold, a valve is actuated to stop flow through the pipe.
One of the problems that U.S. Pat. No. 6,317,051 deals with is how to indicate whether a water flow is “normal” or a leak in the piping system. According to this patent, a second monitor is provided close to the sewer to sense whether the flow of water has continued through the piping system to the sewer. If the flow is sensed at both locations, then it is assumed that there is no leak. If, however, the flow continues in the upstream location, but not near the sewer, this would be indicative of a leak in the system.